Messages in this thread | | | Date | Tue, 17 May 2022 22:02:04 -0700 | Subject | Re: [PATCH V2 Create empty OF root 1/1] of: create empty of root | From | Lizhi Hou <> |
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On 5/16/22 20:22, Frank Rowand wrote: > CAUTION: This message has originated from an External Source. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email. > > > On 2/16/22 23:00, Lizhi Hou wrote: >> Xilinx Alveo PCIe accelerator cards use flattened device tree to describe >> describe apertures in its PCIe BARs. Each device tree node represents an >> aperture and each aperture is an hardware unit which requires a driver. >> The product detail: >> https://www.xilinx.com/products/boards-and-kits/alveo.html >> >> Thus a base device tree is required. Then the Alveo card driver can load >> its flattened device tree and overlay it to the base tree. However device >> tree does not always exist. To resolve this, add OF_EMPTY_ROOT config. >> When it is selected and there is not a device tree, create an empty device >> tree root node. >> > Please run scripts/get_maintainer on your patches to see who to put in > the distribution list. > > I recently stumbled across this patch series and the previous related > patch series (currently up to > "[PATCH V3 XRT Alveo Infrastructure 0/8] XRT Alveo driver infrastructure overview") > when I noticed it in an email archive. Sorry about this. We will use scripts/get_maintainer to make sure the required maintainers are included next time. > > A similar need of creating an of_root if otherwise empty is being discussed > in the thread "[PATCH 0/3] add dynamic PCI device of_node creation for overlay" > at https://lore.kernel.org/r/20220427094502.456111-1-clement.leger@bootlin.com
Thanks a lot for your information. We investigated on adding dt node for PCI device as well and got some questions.
https://lore.kernel.org/lkml/79e4c876-e5a4-861f-cfbc-c75ed1a07ddd@xilinx.com/#t
Thanks,
Lizhi
> > -Frank > >> Signed-off-by: Sonal Santan <sonal.santan@xilinx.com> >> Signed-off-by: Max Zhen <max.zhen@xilinx.com> >> Signed-off-by: Lizhi Hou <lizhi.hou@xilinx.com> >> --- >> drivers/of/Kconfig | 5 ++++ >> drivers/of/Makefile | 1 + >> drivers/of/of_empty_root.c | 51 ++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 57 insertions(+) >> create mode 100644 drivers/of/of_empty_root.c >> >> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig >> index 80b5fd44ab1c..452d2316b47b 100644 >> --- a/drivers/of/Kconfig >> +++ b/drivers/of/Kconfig >> @@ -94,4 +94,9 @@ config OF_DMA_DEFAULT_COHERENT >> # arches should select this if DMA is coherent by default for OF devices >> bool >> >> +config OF_EMPTY_ROOT >> + # driver which requires at least the empty base device tree to >> + # overlay its own device nodes should select this. >> + bool >> + >> endif # OF >> diff --git a/drivers/of/Makefile b/drivers/of/Makefile >> index e0360a44306e..c65364f32935 100644 >> --- a/drivers/of/Makefile >> +++ b/drivers/of/Makefile >> @@ -12,6 +12,7 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o >> obj-$(CONFIG_OF_RESOLVE) += resolver.o >> obj-$(CONFIG_OF_OVERLAY) += overlay.o >> obj-$(CONFIG_OF_NUMA) += of_numa.o >> +obj-$(CONFIG_OF_EMPTY_ROOT) += of_empty_root.o >> >> ifdef CONFIG_KEXEC_FILE >> ifdef CONFIG_OF_FLATTREE >> diff --git a/drivers/of/of_empty_root.c b/drivers/of/of_empty_root.c >> new file mode 100644 >> index 000000000000..5c429c7a27bd >> --- /dev/null >> +++ b/drivers/of/of_empty_root.c >> @@ -0,0 +1,51 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (C) 2022 Xilinx, Inc. >> + */ >> + >> +#include <linux/of.h> >> +#include <linux/slab.h> >> + >> +#include "of_private.h" >> + >> +static int __init of_root_init(void) >> +{ >> + struct property *prop = NULL; >> + struct device_node *node; >> + __be32 *val = NULL; >> + >> + if (of_root) >> + return 0; >> + >> + pr_info("Create empty OF root node\n"); >> + node = kzalloc(sizeof(*node), GFP_KERNEL); >> + if (!node) >> + return -ENOMEM; >> + of_node_init(node); >> + node->full_name = "/"; >> + >> + prop = kcalloc(2, sizeof(*prop), GFP_KERNEL); >> + if (!prop) >> + return -ENOMEM; >> + >> + val = kzalloc(sizeof(*val), GFP_KERNEL); >> + if (!val) >> + return -ENOMEM; >> + *val = cpu_to_be32(sizeof(void *) / sizeof(u32)); >> + >> + prop->name = "#address-cells"; >> + prop->value = val; >> + prop->length = sizeof(u32); >> + of_add_property(node, prop); >> + prop++; >> + prop->name = "#size-cells"; >> + prop->value = val; >> + prop->length = sizeof(u32); >> + of_add_property(node, prop); >> + of_root = node; >> + for_each_of_allnodes(node) >> + __of_attach_node_sysfs(node); >> + >> + return 0; >> +} >> +pure_initcall(of_root_init);
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